Crystal growth, Structural, Optical, Thermal, DFT and Z-scan analyses of Imidazolium Hydrogen Oxalate Crystal for Nonlinear Optical applications

Abstract

Imidazolium Hydrogen Oxalate (IHO) single crystals were grown by the slow evaporation method. The title crystal crystallized in a monoclinic crystal structure with a centrosymmetric space group of P21/n. The 13C and 1H NMR spectra were obtained to understand the molecular structure of the IHO crystal. The 1H NMR contains a peak at 4.90 ppm, which is due to the presence of proton in oxalic acid. The O-H stretching vibration is noted at 3162 cm− 1 in FT-IR and in FT-Raman at 3172 cm− 1. The optical transparency and band gap were evaluated from the UV-Vis-NIR spectrum. The PL spectrum has a high violet emission band at 361nm. TG/DTG study was used to find the thermal stability of the IHO crystal. Hirshfeld surface (HS) analysis revealed the molecular intermolecular interactions in the IHO molecule. The molecular chemical stability of the IHO molecule is determined from the HOMO-LUMO energy gap. The DOS spectrum gives information about the bonding, antibonding, and zero bonding nature present in orbitals, atoms, and molecules. The dipole moment (µ) and total polarizability (α) of the IHO molecule are 13.0268 Debye and 8.2652 x 10− 24 esu, respectively. According to the Mulliken charge distribution, the C11 atom has the highest value, while the O16 atom has the lowest value. The IHO molecule's natural bond orbital (NBO) analysis was performed to ascertain the electron delocalization and conjugative interactions. The third-order nonlinear susceptibility (χ(3)) of the IHO crystal is determined to be 1.1916 x 10− 8 esu.